Techniques and apparatus for selective shaping of mask features using angled beams

ABSTRACT

A method may include providing a set of features in a mask layer, wherein a given feature comprises a first dimension along a first direction, second dimension along a second direction, orthogonal to the first direction, and directing an angled ion beam to a first side region of the set of features in a first exposure, wherein the first side region is etched a first amount along the first direction. The method may include directing an angled deposition beam to a second side region of the set of features in a second exposure, wherein a protective layer is formed on the second side region, the second side region being oriented perpendicularly with respect to the first side region. The method may include directing the angled ion beam to the first side region in a third exposure, wherein the first side region is etched a second amount along the first direction.

RELATED APPLICATIONS

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 62/949,582, filed Dec. 18, 2019, entitled RibbonBeam Plasma Enhanced Chemical Vapor Deposition System for AnisotropicDeposition of Thin Films, and incorporated by reference herein in itsentirety.

FIELD

The present embodiments relate to substrate processing techniques, andmore particularly, to etch processing for patterning structures anddevices.

BACKGROUND

As devices such as a semiconductor devices, optical devices, or deviceselectronic devices, continue to scale to smaller dimensions, the abilityto pattern features becomes increasingly difficult. In addition tochallenging the ability to lithographically define smaller lateral maskfeatures to pattern an underlying substrate or layer to generatefeatures having similar lateral dimension, the maximum thickness of maskfeatures is continuing to shrink to satisfy lithographic requirements.

Moreover, changing the size of such mask features after lithographicpatterning may be useful, such as by etching. For example, to generate agiven array of cavities at a targeted large size and small separationbetween cavities, one possible strategy is to pattern the array ofcavities lithographically to a relatively smaller size with a largerseparation between cavities, and then etch the cavities to enlarge thecavities. In particular, selectively etching a cavity along a givendirection may be useful. Notably, a drawback of etching a cavity formedin a given mask layer is the loss of mask layer thickness during theetching, leading to the inability to pattern an underlying feature afterthe mask etching. Additionally, the cavities may be imperfectly etched,leading to a non-ideal mask shape.

With respect to these and other considerations the present embodimentsare provided.

BRIEF SUMMARY

In one embodiment, a method of patterning a substrate is provided. Themethod may include providing a set of features in a mask layer, the masklayer being disposed on a layer of the substrate, wherein a givenfeature comprises a first dimension along a first direction, a seconddimension along a second direction, orthogonal to the first direction,and a first thickness. The method may also include directing an angledion beam to a first side region of the set of features in a firstexposure, wherein the first side region is etched a first amount alongthe first direction. The method may further include directing an angleddeposition beam to a second side region of the set of features in asecond exposure, wherein a protective layer is formed on the second sideregion, the second side region being oriented perpendicularly withrespect to the first side region. The method may include directing theangled ion beam to the first side region in a third exposure, whereinthe first side region is etched a second amount along the firstdirection.

In another embodiment, a method of patterning a substrate, may includeproviding a set of features in a mask layer, the mask layer beingdisposed on a surface of the substrate and comprising a first material,wherein a given feature comprises a first dimension along a firstdirection, a second dimension along a second direction, orthogonal tothe first direction, and a first thickness. The method may includerepeatedly performing an etch cycle to selectively etch the set offeatures, the etch cycle comprising: directing an angled ion beam to theset of features in a first exposure, when the substrate is oriented at afirst twist angle, wherein the set of features is etch a first amountalong the first direction. The method may also include rotating thesubstrate to a second twist angle after the directing the angled ionbeam, and directing an angled deposition beam the set of features in asecond exposure, wherein a protective layer is formed on a protectedportion of the set of features.

In a further embodiment, an apparatus may include a plasma chamber togenerate a processing plasma, and a substrate stage, to support asubstrate, and disposed adjacent to the plasma chamber. The apparatusmay also include an extraction assembly, disposed along a side of theplasma chamber, between the plasma and the substrate stage, to extractplasma species from the plasma, and a bias voltage source to apply abias voltage between the plasma chamber and the substrate. The apparatusmay include a controller to send a first control signal to the biasvoltage source to apply a first bias voltage between the plasma chamberand the substrate while the substrate stage is arranged at a first twistangle. The controller may be arranged to send a second control signal tothe bias voltage source to apply second bias voltage between the plasmachamber and the substrate, the second bias voltage being less inabsolute magnitude than the first bias voltage, and to send concurrentlywith the second control signal, a third control signal to rotate thesubstrate stage to a second twist angle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-5C generally depict the structure of a substrate at differentstages of processing, according to embodiments of the presentdisclosure;

FIG. 1A depicts a top view of a substrate after patterning to form amask layer;

FIG. 1B depicts a side cross-sectional view of the substrate of FIG. 1A;

FIG. 1C depicts an end cross-sectional view of the substrate of FIG. 1A;

FIG. 2A depicts a top view of the substrate of FIG. 1A, subsequent tothe instance of FIG. 1A, after processing by an ion beam;

FIG. 2B depicts a side cross-sectional view of the substrate of FIG. 2A;

FIG. 2C depicts an end cross-sectional view of the substrate of FIG. 2A;

FIG. 3A depicts a top view of the substrate of FIG. 1A, subsequent tothe instance of FIG. 2A, after processing by a deposition beam;

FIG. 3B depicts a side cross-sectional view of the substrate of FIG. 3A;

FIG. 3C depicts an end cross-sectional view of the substrate of FIG. 3A;

FIG. 3D depicts an enlarged view of a portion of the substrate of FIG.3C;

FIG. 3E depicts an example of directional deposition beam processing ofa set of patterned features, consistent with embodiments of thedisclosure;

FIG. 4A depicts a top view of the substrate of FIG. 1A, subsequent tothe instance of FIG. 3A, after further processing by an ion beam;

FIG. 4B depicts a side cross-sectional view of the substrate of FIG. 4A;

FIG. 4C depicts an end cross-sectional view of the substrate of FIG. 4A;

FIG. 5A depicts a top view of the substrate of FIG. 1A, subsequent tothe instance of FIG. 4A, after further processing;

FIG. 5B depicts a side cross-sectional view of the substrate of FIG. 5A;

FIG. 5C depicts an end cross-sectional view of the substrate of FIG. 5A;

FIG. 5D and FIG. 5E shown an example of processing during a given etchcycle, according to further embodiments of the disclosure;

FIG. 6A depicts a top view of the substrate of FIG. 1A, illustrating atargeted mask pattern after directional etching;

FIG. 6B depicts a side cross-sectional view of the substrate of FIG. 6Aafter directional etching using an ion beam, while not employing adeposition beam;

FIG. 6C depicts an end cross-sectional view of the substrate of FIG. 6B;

FIG. 7A depicts a side view of a processing apparatus during ion beamprocessing of a substrate, in accordance with embodiments of the presentdisclosure;

FIG. 7B depicts a to view of a portion of the processing apparatus ofFIG. 7A, during the instance depicted in FIG. 7A;

FIG. 7C depicts a side view of a processing apparatus during depositionbeam processing of a substrate, in accordance with embodiments of thepresent disclosure;

FIG. 7D depicts a to view of a portion of the processing apparatus ofFIG. 7A, during the instance depicted in FIG. 7C;

FIG. 7E, FIG. 7F, and FIG. 7G depict aspects of another apparatus,according to embodiments of the present disclosure;

FIG. 8 depicts the geometry for changing the shape of a patternedfeature by combined directional ion beam processing and directionaldeposition beam processing, according to an embodiment of thedisclosure;

FIG. 9 depicts the geometry for generating a composite merged shape bymerging multiple patterned features using a combined directional ionbeam processing and directional deposition beam processing, according toanother embodiment of the disclosure;

FIG. 10 depicts an exemplary process flow, according to one embodiment;

DETAILED DESCRIPTION

The present embodiments will now be described more fully hereinafterwith reference to the accompanying drawings, where some embodiments areshown. The subject matter of the present disclosure may be embodied inmany different forms and are not to be construed as limited to theembodiments set forth herein. These embodiments are provided so thisdisclosure will be thorough and complete, and will fully convey thescope of the subject matter to those skilled in the art. In thedrawings, like numbers refer to like elements throughout.

This present embodiments provide novel techniques and apparatus topattern substrates and in particular novel techniques to etch a cavitydisposed in a substrate, along a designed direction. In variousembodiments, a feature such as a via or trench may be formed having aninitial shape and size, and may be subsequently elongated along thedesigned direction using a series of etch operations. The designeddirection may correspond to a horizontal direction within a plane of thesubstrate. According to various embodiments, the elongation of thefeature may take place along the designed direction (first direction)while the cavity is not enlarged or enlarged to a lesser extent along aperpendicular direction to the designed direction (second direction)within the plane of the substrate. In this manner, a cavity may beselectively elongated along just one direction, providing variousconcomitant advantages for patterning substrates, as disclosed herein.

According to the embodiments disclosed herein, a mask having a set ofpatterned features may be processed in an iterative fashion toselectively etch mask features and selectively deposit a protectivelayer of material or replenishment material to avoid unwanted etching ofthe mask features in certain portions of the mask features. In someembodiments, a directional ribbon beam is employed to iterativelyprocess etch a patterned feature. The iterative processing may involverepeating a directional etch operation that is interspersed with adirectional deposition operation. In one example, a processing operationmay involve etching certain regions of a patterned feature of a mask,such as a sidewall or endwall of a cavity in a desired direction,followed by rotation of the mask, and directional deposition ofprotective or replenishing layer on other regions of the mask. After thedirectional deposition, the mask may be rotated back to an originalposition, and directional etching of the cavity or other patternedfeature along the desired direction resumed. In this manner, thepatterned feature of the mask may be etched to a desired length along adesired direction, while preventing unwanted etching of patternedfeatures that may otherwise occur during prolonged directional etchingalong a specific direction. According to some embodiments, disclosedbelow, the iterative directional etching and direction deposition may beperformed on a mask, using a common processing plasma chamber, wherebiasing between a substrate containing the mask and the plasma chamberis switched from negative bias to zero bias between the directionetching operation and direction deposition operation, respectively.

In different embodiments of the disclosure, directional deposition anddirectional etching may be performed using a common plasma chamber toextract directional beams, where the directional deposition employs thesame chemistry as the directional etching, where directional depositionis accomplished by decreasing the bias between plasma chamber andsubstrate, as compared to the bias applied to generate the directionaletching. As an example, plasma species including ions may be extractedfrom the plasma chamber to form an ion beam to perform directionaletching using a relatively high bias, while plasma species includingradicals, neutrals, and possibly ions may be extracted from the plasmachamber to form a deposition beam to perform directional depositionusing a relatively low bias or zero bias.

Turning now to the figures, FIGS. 1A-5C generally depict the structureof a substrate at different stages of processing, according toembodiments of the present disclosure. According to various embodiments,as shown in the FIGS. 1A-5C, a selective etching operation is performedusing a combination of a deposition operation and an etch operation thatare performed in a sequential and iterative manner. FIG. 1A depicts atop view of a substrate after patterning to form a mask layer, whileFIG. 1B depicts a side cross-sectional view of the substrate of FIG. 1A,and FIG. 1C depicts an end cross-sectional view of the substrate of FIG.1A. In FIG. 1A, a substrate 100 is shown, including a mask layer 112that defines a mask having an array of patterned features, in thisexample, a set of cavities, shown as cavities 106. The mask layer 112 isdisposed on other parts of a substrate, such as a layer 114, subjacentthe mask layer 112, and a layer 116, subjacent the layer 114.

According to various embodiments of the disclosure, the mask layer 112may be a photoresist material, a hard mask material, a carbon material,an oxide such as silicon oxide, a nitride such as silicon nitride, orother suitable mask material. The mask layer 112 may be used to mask thelayer 114, so that the pattern of cavities 106 may be transferred intothe layer 114, for example, by a known etching process, such as reactiveion etching (RIE). In various embodiments, the layer 114 may be adifferent material than the material of mask layer 112. For example, themask layer 112 may be formed of silicon nitride or carbon, while thelayer 114 is formed of silicon or silicon oxide. Likewise the layer 116may be a different material than the material of layer 114. For example,the layer 114 may be formed of silicon oxide, while the layer 116 isformed of silicon. The embodiments are not limited in this context.

In the present embodiments, before transferring of the pattern of themask layer 112 into the layer 114, the mask layer 112 may be processedto selectively change the pattern of the mask layer 112, for example toselectively change the dimensions of the cavities 106, to change thespacing between cavities 106, and so forth. For example, devicepatterning of the substrate 100 may call for the cavities 106 to beseparated by a tip-to-tip spacing, shown as S2, in FIG. 5A. Afterlithographic patterning, the mask layer 112 may exhibit a tip-to-tipspacing shown as S1. In some instances, lithographic patterning may belimited to image spacings between adjacent cavities less than a givenamount, such as S1, along the Y-direction of the Cartesian coordinatesystem shown. For example, the value of S1 may be on the order of a fewnanometers, or a few tens of nanometers, where lithographic patterningmay not resolve spacings smaller than S1 within the mask layer 112. Forthis reason, the mask layer 112, after patterning to generate thepattern of FIG. 1A, having the length of cavities of L1 and separationof S1 along the Y-direction, may be subjected to selective etching anddeposition processes, to change the dimension of the cavities, thespacing between cavities, long at least one direction, and in some casesto change the shape of the cavities. Such combined etching anddeposition processes may be referred to herein as selectively shaping apatterned feature, such as a cavity.

At a subsequent instance, FIG. 2A depicts a top view of the substrate ofFIG. 1A, after processing by an angled ion beam 120. FIG. 2B depicts aside cross-sectional view of the substrate of FIG. 2A, while FIG. 2Cdepicts an end cross-sectional view of the substrate of FIG. 2A. At theinstance of FIG. 2A, the angled ion beam 120 is directed to a first sideregion of the set of features of the mask layer 112, meaning a sideregion of the cavities 106. The first side region may represent asidewall, an endwall, a portion of a sidewall in various non-limitingembodiments. In this example, the first side region of the cavities 106is represented by endwalls 106A. In various non-limiting embodiments,the cavities 106 may be trenches that are elongated along the Y-axis. Assuch, the angled ion beam may etch the endwalls 106A a first amountalong a first direction, parallel to the Y-axis. Notably, the angled ionbeam 120 may be directed as an angled reactive ion beam to the substrate100 at a non-zero angle of incidence (shown as Be) with respect to aperpendicular 132 to a main plane P of the substrate 100, where the mainplane may be represented by the X-Y plane. Thus, the angled ion beam 120may directly impact the endwalls 106A as shown. In differentnon-limiting embodiments of the disclosure, the value of may varybetween 5 degrees and 85 degrees, and in particular embodiments between15 degrees and 60 degrees.

The angled ion beam 120 may be provided using a known etch chemistrychosen according to the nature of the mask layer 112, as well as thelayer 114. For example, if the mask layer 112 is an SiN layer, the etchchemistry may be chosen to selectively etch SiN with respect to othermaterials, such as the material of layer 114, which layer may be siliconoxide. In some embodiments, the etch operation involves directing a pairof an angled reactive ion beams at a non-zero angle of incidence wherethe two angled reactive ion beams have a value represented by +/−(θc)and form mirror image with respect to the X-Z plane, as shown. As such,a pair of endwalls 106A, opposing one another, may be etched. As furthershown also in FIG. 1B, for example, the cavities 106 of mask layer 112may be selectively etched along the Y-direction so as to reduce thespacing between adjacent cavities along the Y-direction to a value ofS2, less than S1. As such, the cavities 106 are also elongated along theY-direction to a value of L2. Notably, during the etch operation of FIG.2A-2C, the height of the mask layer 112 along the Z-axis may be reducedfrom the value of h1.

Notably, the angle of incidence of the angled ion beam 120 and durationof the etching during the instance of FIGS. 2A-2C may be limited tolimit removal of the mask layer material of mask layer 112 from the topsurface of the mask layer 112, and to prevent widening of the cavities106 along the X-direction. For example, as shown in FIG. 2C, thecavities 106 may retain the original dimension, shown as W1, along theX-direction.

Turning to FIG. 3A there is shown a top view of the substrate of FIG.1A, subsequent to the instance of FIG. 2A, after processing by adeposition beam, in accordance with the present embodiments. FIG. 3Bdepicts a side cross-sectional view of the substrate of FIG. 3A, whileFIG. 3C depicts an end cross-sectional view of the substrate of FIG. 3A,and FIG. 3D depicts an enlarged view of a portion of the substrate ofFIG. 3C.

In FIG. 3A, an angled deposition beam 140 is directed to a second sideregion of the mask set of features of mask layer 112, meaning thesidewalls 106B of the cavities 106, in a second exposure. As such, aprotective layer 134 is formed on the second side region. In thisexample, the second side region encompasses an upper portion of thesidewalls 106B. The protective layer 134 is also formed on the topsurface of the mask layer 112. The protective layer 134 may be formed bydirecting the angled deposition beam 140 at a second non-zero angle ofincidence with respect to the perpendicular 132, where the secondnon-zero angle of incidence of angled deposition beam 140 is representedby θ_(D). Depending upon the aspect ratio of the cavities 106 along theX-Z plane shown in FIG. 3C, as well as the value of the second non-zeroangle of incidence, the extent of coverage of the sidewalls 106B may begreater or lesser. Notably, in the example of FIGS. 3A-3C, theorientation of the mask layer 112 is rotated 90 degrees about theperpendicular 132 with respect to the orientation of the mask layer 112in FIG. 2A. Thus, the angled deposition beam 140 is directed at anon-zero angle with respect to the Y-Z plane in the instance of FIGS.3A-C while the angled ion beam 120 is provided at a non-zero angle ofincidence with respect to the X-Z plane in the instance of FIGS. 2A-2C.FIG. 3E depicts an example of directional deposition beam processing ofa set of patterned features 131, consistent with embodiments of thedisclosure, where a protective layer 134A is deposited just on rightsidewalls and upper surfaces, by directing an angled beam from the upperright of the figure.

By providing the protective layer 134 over sidewalls 106B and over thetop surface of the mask layer 112, the mask layer 112 may be selectivelyreplenished to prevent etching in unwanted portions of the mask layer.In particular embodiments, the replenishing provided by the protectivelayer 134 may be tuned to balance out or replace the same amount ofmaterial that is removed from certain surfaces by unwanted etchingduring the etch operation of FIGS. 2A-2C. For example, the amount ofmaterial deposited in the select regions where protective layer 134forms, may be tuned to equal the amount of etching taking place in theseselect regions during a given etch operation. Thus, the protective layer134 may be deposited on top surfaces of the mask layer 112 to a layerthickness that matches the amount of material removed from the topsurface of the mask layer 112 during the etching operation of FIG. 2A,with the net result that the thickness of mask layer 112 remainsconstant after each cycle of etching and layer deposition. Likewise, theamount of material of the protective layer 134 deposited on sidewalls106B may be tailored to match and replenish the amount of material ofmask layer 112 that is removed from sidewalls 106B during a previousetch operation. Of course, net material will be removed from targetedsurfaces of the mask layer, such as the endwalls 106A. Notably, therelative duration of the deposition operation of FIG. 3A may be adjustedaccording to the duration of etch operation of FIG. 2A, depending uponrelative deposition rates and etch rates.

Subsequently to the operation of FIGS. 3A-3E, an etching operationsimilar to the operation of FIGS. 2A-2C may be repeated to furtherelongate the cavities 106 along the Y-axis. FIG. 4A depicts a top viewof the substrate of FIG. 1A, subsequent to the instance of FIG. 3A,after further processing by an angled ion beam. FIG. 4B depicts a sidecross-sectional view of the substrate of FIG. 4A, while FIG. 4C depictsan end cross-sectional view of the substrate of FIG. 4A. In thisexample, the angled ion beam 120 is directed to the first side region,meaning a portion of the endwalls 106A, in a third exposure, wherein thefirst side region is etched a second amount along the first direction,that is, along the Y-axis. The angled ion beam 120 may represent thesame conditions as the conditions of angled ion beam 120 in FIG. 2Aaccording to one embodiment. Notably, in the example of FIGS. 4A-4C, theorientation of the mask layer 112 may be rotated −90 degrees about theperpendicular 132 with respect to the orientation of the mask layer 112in FIG. 3A, and thus back to the original orientation of the angled ionbeam 120 with respect to mask layer 112, as shown in FIG. 2A. At thisstage, the separation of the cavities 106 may be at a value S3, whichvalue may be a targeted value for the separation of the cavities. Assuch, further directional etching along the Y-axis of cavities 106 maycease.

In some embodiments a portion of the protective layer 134 may remainafter the operation of FIG. 4A, as suggested in FIGS. 4A-4C. In exampleswhere the material of protective layer 134 is different from thematerial of mask layer 112, the protective layer may be subsequentlyremoved, for example by known selective etching techniques. In otherembodiments, residual amounts of protective layer 134 may not be removedbefore subsequent etching of the layer 114 using mask layer 112. Forexample, the mask layer 112 and protective layer 134 may be formed fromthe same hard mask material. During the etch process of FIG. 4A, anappropriate amount of protective layer 134 may be removed to render thedimensions of cavities 106 and the spacing between cavities 106 atdesired values.

FIG. 5A depicts a top view of the substrate of FIG. 1A, subsequent tothe instance of FIG. 4A, after further processing. FIG. 5B depicts aside cross-sectional view of the substrate of FIG. 5A, while FIG. 5Cdepicts an end cross-sectional view of the substrate of FIG. 5A. In thisexample, any residual portion of the protective layer 134 has beenremoved, rendering the mask layer 112 with the dimension of L3 for thecavities 106 and S3 for separation between cavities 106. Additionally,the width of cavities 106 along the X-axis remains at W1, the same valueas the original width of the cavities 106.

Notably in the embodiments, of FIGS. 1A-5C, directional etching anddeposition processes may be alternated with one another in a cyclicfashion, through multiple etch cycles, where a given etch cycle involvesthe following set of operations. The etch cycle may start with 1)directing an angled ion beam to the set of features in a first exposure,when the substrate is oriented at a first twist angle, wherein the setof features is etch a first amount along a first direction; 2) rotatingthe substrate to a second twist angle after the directing the angled ionbeam; and directing an angled deposition beam the set of features in asecond exposure, wherein a protective layer is formed on a protectedportion of the set of features. In various embodiments, the second twistangle may be a 90 degree rotation about a perpendicular to a main planeof the substrate, with respect to the first twist angle. In this way,the angled deposition beam will tend to strike regions of a surfacefeature that are oriented perpendicularly with respect to those regionsof the surface feature that are impacted by the directional ion beam.According to some embodiments, an etch cycle may be repeated 5 times, 10times, 20 times or more, depending upon the extent of etching to beperformed. For example, to selectively elongate a cavity by 10 nm alongan X-direction, a given etch process using an angled ion beam within agiven etch cycle may remove 0.5 nm of an endwall along the X-direction,while a given deposition process using an angled deposition beam maydeposit a protective layer having a thickness on the order of 0.2 nm. Toelongate the cavity by 10 nm may therefore require 20 etch cycles. As agiven etch cycle proceeds, a portion of cavity sidewalls and top surfaceof a mask layer may be continually replenished before faceting orrounding may take place.

In one variant of the processes depicted at FIGS. 1A-5C, multiple cyclesmay be performed where a given cycle includes an angled directionaletching operation and angled directional deposition, in a manner thatafter a given cycle the structure and shape of a mask are preserved, asdiscussed above. Turning to FIG. 5D and FIG. 5E, there is shown anexample of processing during a given etch cycle, where the structure ofFIG. 5D represents a mask layer 112 after directional etching asgenerally discussed with respect to FIG. 2A-2C, and the structure ofFIG. 5E depicts the mask layer 112 from an end cross-section afterreplenishment by a directional deposition as generally discussed withrespect to FIGS. 3A-3E. The dashed line in FIG. 5D outlines a depletionzone 112A, showing the contours of the original state of mask features112B that define the cavities 106 before etching, as well as the presentsurface of mask features 112B of the mask layer 112 after etching,revealing that a certain amount of material has been removed from a topsurface 106T of the mask layer 112, as well as from sidewalls 106B. Asshown in FIG. 5E, the directional deposition has replenished the masklayer 112, so the cavities 106 of mask layer 112 retains the originaldimensions and shape in terms of h1 and w1. This process may be repeatedfor any number of cycles so that the mask features are repeatedlyreplenished to original shape and size within the X-Z plane, while themask features 112B are progressively etched along the Y-axis toselectively elongate the cavities 106. In this manner, the finaloperation of a series of etch cycles may be represented by FIG. 5E,where the deposition layer 134B may be a different material or the samematerial as mask layer 112. At this stage, the mask layer 112 may thenbe used without further processing to etch the underlying layer, layer114.

To highlight the advantages of the embodiments as shown in FIG. 1A-5C,FIGS. 6A-6C illustrate an example of directional etching used toelongate a cavity, while not using directional deposition. Inparticular, FIG. 6A depicts a top view of the substrate of FIG. 1A,illustrating a targeted mask pattern after directional etching. FIG. 6Bdepicts a side cross-sectional view of the substrate of FIG. 6A afterdirectional etching using an ion beam, while not employing a depositionbeam, and FIG. 6C depicts an end cross-sectional view of the substrateof FIG. 6B. In FIG. 6A, the mask layer 112 is shown generally as in FIG.1A, with the addition of a targeted mask pattern 106D, where thecavities 106 are elongated to the dimension L3 by employing the angledion beam 120, without using angled deposition beam 140, discussed above.In this example, as shown in FIG. 6B and FIG. 6C, the mask layer 112 maybe eroded to exhibit rounding or faceting along sides of the cavities106, including along the X-Z plane, shown in FIG. 6C. Because of thiserosion, poor pattern transfer may take place when pattern transfer ofthe mask pattern of mask layer 112 takes place by etching the layer 114.

In some embodiments, the aforementioned processes may be performed usinga ribbon beam-type processing system, where an angled ion beam and/or anangled deposition beam is provided having a ribbon beam shape, where theribbon cross-section is elongated along one direction with respect to anorthogonal direction.

FIG. 7A depicts a side view of a processing apparatus 200 during ionbeam processing of a substrate, in accordance with embodiments of thepresent disclosure. FIG. 7B depicts a top view of a portion of theprocessing apparatus of FIG. 7A, during the instance depicted in FIG.7A. FIG. 7C depicts a side view of a processing apparatus duringdeposition beam processing of a substrate, in accordance withembodiments of the present disclosure. FIG. 7D depicts a to view of aportion of the processing apparatus of FIG. 7A, during the instancedepicted in FIG. 7C.

As to the general features of the processing apparatus 200, thisapparatus represents a processing apparatus for selectively etchingprocessing portions of a substrate, such as selectively elongating acavity. The processing apparatus 200 may be a plasma-based processingsystem having a plasma chamber 202 for generating a plasma 204 thereinby any convenient method as known in the art. A power supply 230, may,for example, be an RF power supply to generate the plasma 204. Anextraction plate 206 may be provided as shown, having an extractionaperture 208, where a selective etching may be performed to selectivelyremove sidewall layers. A substrate, such as a substrate 100 having theaforementioned structure as shown at FIGS. 1A-1C, is disposed in theprocess chamber 222. A substrate plane of the substrate 100 isrepresented by the X-Y plane of the Cartesian coordinate system shown,while a perpendicular to the plane of the substrate 100 lies along theZ-axis (Z-direction).

As further shown in FIG. 7A, a controller 240 may be provided to sendcontrol signals to the bias supply 220 and to the substrate stage 214.

In one example, the view of FIG. 7A may represent a variant of theselective etching operation shown in FIG. 1B, for example. During adirectional etching operation, a plasma, such as a reactive plasma isformed using a reactive chemistry in the plasma chamber 202, and anangled ion beam 120 is extracted as a pair of ion beams, as shown.Notably, the processing apparatus 200 includes a beam blocker 232,disposed adjacent the extraction aperture 208. The beam blocker 232 issized and positioned to define a first aperture 208A and a secondaperture 208B, where the first aperture 208A forms a first angled ionbeam 120A, and the second aperture 208B forms a second angled ion beam120B. The two angled ion beams may define angles of incidence withrespect to the perpendicular 132, equal in magnitude, opposite indirection. In one embodiment, the first angled ion beam 120A and thesecond angled ion beam 120B may represent an angled reactive ion beam.The beam blocker offset along the Z-axis with respect to extractionplate 206 may help define the angle of the angled ion beams.

In particular, as shown in FIG. 7A, and with reference to the geometryof FIGS. 2A-2C, the angled ion beam 120, forming a non-zero angle ofincidence with respect to the Z-axis (normal to the substrate plane),may strike the regions of cavities 106 oriented along the X-Z plane, asnoted. As such, the first angled ion beam 120A and the second angled ionbeam 120B may selectively etch the endwalls 106A, while not etching thesidewalls 106B (oriented along the Y-Z plane), and thus selectivelyelongate of the cavities 106 to generate the elongated structure ofcavities 106, as shown in FIG. 5A to FIG. 5C.

In the example of FIG. 7B, the angled ion beam 120 is provided as a pairof ribbon ion beams that are formed by an elongated extraction aperture,extending to a beam width along the X-direction, where the beam width isadequate to expose an entire width of the substrate 100, even at thewidest part along the X-direction. Exemplary beam widths may be in therange of 10 cm, 20 cm, 30 cm, or more while exemplary beam lengths alongthe Y-direction may be in the range of 3 mm, 5 mm, 10 mm, or 20 mm. Theembodiments are not limited in this context.

The angled ion beams 120 may be extracted when a voltage difference isapplied using a bias voltage source, shown as bias supply 220, betweenthe plasma chamber 202 and substrate 100 as in known systems. The biassupply 220 may be coupled to the process chamber 222, for example, wherethe process chamber 222 and substrate 100 are held at the samepotential. In various embodiments, the angled ion beam 120 may beextracted as a continuous beam or as a pulsed ion beam as in knownsystems. For example, the bias supply 220 may be configured to supply avoltage difference between plasma chamber 202 and process chamber 222,as a pulsed DC voltage, where the voltage, pulse frequency, and dutycycle of the pulsed voltage may be independently adjusted from oneanother. When configured in the shape of a ribbon beam as in FIG. 7B,these angled ion beams may expose an entirety of the substrate 100 toreactive ion etching of the cavities 106 distributed in devices acrossthe substrate 100, by scanning the substrate platen 214 along the scandirection 216, as shown.

In various embodiments, the value of the non-zero angle of incidence mayvary from 5 degrees to 85 degrees, while in some embodiments the valuemay range between 15 degrees and 60 degrees. The embodiments are notlimited in this context. The angled ion beam 120 may be composed of anyconvenient gas mixture, including inert gas, reactive gas, and may beprovided in conjunction with other gaseous species in some embodiments.Gas may be provided from a gas source 224, where the gas source 224 maybe a gas manifold coupled to provide a plurality of different gases tothe plasma chamber 202. In particular embodiments, the angled ion beam120 and other reactive species may be provided as a predetermined etchrecipe to the substrate 100 so as to perform a directed reactive ionetching of targeted sidewalls of patterning layers on substrate 100. Asdiscussed above, the etch recipe may be selective with respect to thematerial of the layer 114, so as to remove material of the mask layer112, while not etching the layer 114, or etching the layer 114 to alesser extent.

FIG. 7C and FIG. 7D depict a subsequent instance of processing thesubstrate 100, generally as discussed above with respect to FIGS. 4A-4C.In this instance, the processing apparatus 200 generates angleddeposition beam 140, as a first angled deposition beam 140A and a secondangled deposition beam 140B, using the same extraction geometry asdiscussed above with respect to FIGS. 7A and 7B. Notably, in thisinstance, the substrate stage 214 has been rotated through a twist angleof 90 degrees with respect to the configuration of FIG. 7A and FIG. 7B.

In one implementation, the angled deposition beam 140 may be generatedusing the same conditions as generating the angled ion beam 120,discussed above, save for a change in the bias applied between theplasma chamber 202 and the substrate 100. For example, to generate theangled ion beam 120, a −500 V bias may be applied between the substrate100 and plasma chamber 202, to extract a reactive ion beam having ionswith energies in the range of 500 eV for singly charged positive ions.As such, during a reactive ion etching process, the net result ofcompeting processes of etching the mask layer 112 and depositing apolymer film on the mask layer 112, may be to etch the mask layer 112,due to the energy of the ions of angled ion beam 120. In the example ofFIG. 7C, the angled deposition beam may 140 be generated by reducing thebias between plasma chamber 202 and substrate 100 to a value of −50 V,for example, or 0 V, wherein the energy of any ions present in theangled deposition beam 140 will be much less than in the etching processof FIG. 7A, favoring a net deposition due to radicals, and otherpolymer-forming species in the angled deposition beam 140.

In some embodiments, using processing apparatus 200, the substrate 100may be scanned along the Y-direction for at least one scan with a highbias voltage applied, followed by rotating the substrate 100 through 90degrees about the perpendicular 132 within the X-Y plane, accompanied byreducing the level of or extinguishing the bias voltage, and scanningthe substrate 100 along the Y-direction for at least one additionalscan. This sequence of operations may be repeated through multiplecycles to selectively etch surface features of a mask layer along agiven direction, while avoiding unwanted mask loss, rounding, faceting,and other side effects generated during continuous etching without theuse of the angled deposition of the present embodiments.

While the embodiments of FIGS. 7A-7D depict a single plasma chamber, inother embodiments, two plasma chambers may be provided, wherein a firstplasma chamber is used to direct an angled ion beam to the substrate,and a second plasma chamber is used to direct an angled deposition beamto the substrate. The substrate may be transported between positionsadjacent the first plasma chamber and second plasma chamber to performan etch cycle. An advantage of this latter configuration is that thesecond plasma chamber may be configured with an extraction assembly thatdirects the deposition beam to the substrate at a different angle ofincidence than the angle of incidence used for the angled ion beam,producing increased process flexibility. Additionally, different plasmachemistry may be employed in the deposition beam plasma chamber asopposed to the ion beam plasma chamber, so that a substrate may beprocessed rapidly by subjecting the substrate to an etch chemistrydifferent than the deposition chemistry, without incurring process delaythat may occur to switch chemistry within a common plasma chamber.

FIG. 7E, FIG. 7F, and FIG. 7G depict aspects of another apparatus,according to embodiments of the present disclosure. The apparatus 250includes a cylindrical plasma chamber, shown as plasma chamber 252,elongated along the X-axis, and including an elongated aperture, shownas extraction aperture 208, where the extraction aperture 208 is boundedby a nozzle structure 254 that extends radially outwardly from theplasma chamber 252. In various non-limiting embodiments, the plasmachamber 252 may be rotatable about the X-axis, the substrate stage 214may be tiltable about the X-axis, may be scannable along the Y-axis, androtatable about the Z-axis. As such, the aforementioned operations ofdirectional angled etching and directional angled deposition may beperformed by alternately applying a bias voltage between the plasmachamber 252 and substrate stage 214 during a first exposure and removingthe bias voltage between substrate stage 214 and plasma chamber 252during a second exposure, while also rotating the substrate stage 214 90degrees about the Z-axis between the first exposure and the secondexposure. An advantage provided by the apparatus 250 is that the nozzlestructure 254 may tend to collimate a deposition beam having neutralradicals that otherwise may tend to diverge after exiting the plasmachamber 252, thus preserving and improving directionality of adeposition beam used to selectively deposit a protection layer.

FIG. 8 depicts the geometry for changing the shape of a patternedfeature by combined directional ion beam processing and directionaldeposition beam processing, according to an embodiment of thedisclosure. In this example, directional etching and directionaldeposition processes may be combined as generally described with respectto FIGS. 1A to 5C, except in this instance a substrate 300 is providedwith a mask layer 301 having a series of cavities shaped as vias orcircles. By performing the operations of FIGS. 2A to 5C, the cavities302 may be selectively elongated along the Y-direction to form trenches304, where directional etching is interspersed with directionaldeposition in a direction orthogonal to the directional etching whenviewed in the X-Y plane, as shown. As such, rounding or faceting of thetrenches 304 may be avoided.

FIG. 9 depicts the geometry for generating a composite merged shape bymerging multiple patterned features using a combined directional ionbeam processing and directional deposition beam processing, according toanother embodiment of the disclosure. In this example, directionaletching and directional deposition processes may be combined asgenerally described with respect to FIGS. 1A to 5C, except in thisinstance a substrate 400 is provided with a mask layer 401 having aseries of cavities shaped as trenches 402, offset from one another in astaggered fashion as shown. By performing the operations of FIGS. 2A to5C, the trenches 402 may be selectively elongated along the X-directionto form a merged shape 404, where directional etching is interspersedwith directional deposition in a direction orthogonal to the directionaletching when viewed in the X-Y plane, as shown. As such, rounding orfaceting of mask surfaces during formation of the merged shape 404 maybe avoided.

FIG. 10 depicts an exemplary process flow 500, according to oneembodiment of the disclosure. At block 502, a set of features isprovided in a mask layer. A given feature of the set of features may becharacterized by a first dimension along a first direction. In oneexample a cavity formed in a mask layer may have a first length along agiven direction.

At block 504, an angled ion beam is directed to a first side region ofthe set of features during a first exposure. The first side region mayconstitute an endwall of a cavity according to various embodiments. Assuch, the first side region is etched a first amount along the firstdirection.

At block 506, an angled deposition beam is directed to a second sideregion of the set of features in a second exposure, where the secondside region being is oriented perpendicularly with respect to the firstside region. For example, the second side region may constitute an upperportion of sidewalls of a cavity whose endwalls are etched in theoperation of block 404. As such, a protective layer is formed on thesecond side region.

At block 508 an angled ion beam is directed to the first side region ina third exposure, wherein the first side region is etched an additionalamount along the first direction.

The flow then proceeds to decision block 510, where a determination ismade as to whether a final or target dimension is reached. If so, theflow proceeds to block 512, where the mask layer is used to etch asubjacent layer, If not, the flow returns to block 506.

Notably, in the aforementioned embodiments, examples of using a commonplasma chamber and a common plasma chemistry have been detailed.However, in other embodiments, a different chamber may be used toprovide a deposition beam to a substrate. For added flexibility, areactive etching ion beam could be provided using a CFx etch chemistry,while a deposition beam is provided with a different chemistry todeposit, for example, a C, SiO₂, SiN, or other material. While addingflexibility, this approach may entail switching of gases provided to aplasma chamber, between rotations, and would add to process time.

Moreover, while the aforementioned embodiments illustrate the iterativeuse of angled ion beam etching and angled ion beam deposition, with theused of substrate rotation between etching and deposition, the relativeamount of etching or deposition within a given operation may depend uponthe application, where, for a given mask layer, and subjacent layer,experimentation may be used to determine the balance between depositionand erosion for each iteration or cycle of deposition and etch. Forinstance there could be one substrate scan for deposition performed forevery ten etching scans, or the reverse where one etching scan isperformed for every 10 deposition scans, depending on the etchchemistry, ion bias, etc.

The present embodiments provide various advantages over conventionalprocessing to define features in a substrate. One advantage lies in theability to selectively elongate a cavity along just one direction, whilepreserving the dimension of the cavity along a second direction,perpendicular to the first direction. Another advantage is the abilityto reduce cavities below the spacing achieved by known lithographyprocesses. An example of this ability is the reduction of tip-to-tipseparation between adjacent trenches such as contact trenches. Anotheradvantage provided by the present embodiments is the ability to preventundue thickness loss of a hardmask and reduce corner rounding in acavity formed in the hardmask layer, while still selectively elongatingthe cavity along a targeted direction. A further advantage is theability to reduce the number of masks used to generate a pattern offeatures, where the features may be separated by a distance less thanthe threshold separation achievable by a single mask. This reducing thenumber of masks has the further advantageous effect of reducing overlayerror for printing the pattern of features.

The present disclosure is not to be limited in scope by the specificembodiments described herein. Indeed, other various embodiments of andmodifications to the present disclosure, in addition to those describedherein, will be apparent to those of ordinary skill in the art from theforegoing description and accompanying drawings. Thus, such otherembodiments and modifications are in the tended to fall within the scopeof the present disclosure. Furthermore, the present disclosure has beendescribed herein in the context of a particular implementation in aparticular environment for a particular purpose, while those of ordinaryskill in the art will recognize the usefulness is not limited theretoand the present disclosure may be beneficially implemented in any numberof environments for any number of purposes. Thus, the claims set forthbelow are to be construed in view of the full breadth and spirit of thepresent disclosure as described herein.

1. A method of patterning a substrate, comprising: providing a set offeatures in a mask layer, the mask layer being disposed on a layer ofthe substrate, wherein a given feature comprises a first dimension alonga first direction, a second dimension along a second direction,orthogonal to the first direction, and a first thickness; directing anangled ion beam to a first side region of the set of features in a firstexposure, wherein the first side region is etched a first amount alongthe first direction; directing an angled deposition beam to a secondside region of the set of features in a second exposure, wherein aprotective layer is formed on the second side region, the second sideregion being oriented perpendicularly with respect to the first sideregion; and directing the angled ion beam to the first side region in athird exposure, wherein the first side region is etched a second amountalong the first direction.
 2. The method of claim 1, the directing theangled ion beam comprising: forming a reactive plasma in a plasmachamber; applying a bias voltage between the substrate and the plasmachamber; and extracting the angled ion beam from the reactive plasmathrough an extraction assembly, and directing the angled ion beam as anangled reactive ion beam to the substrate at a non-zero angle ofincidence with respect to a perpendicular to a main plane of thesubstrate.
 3. The method of claim 2, the directing the angled depositionbeam comprising: after the first exposure, setting the substrate andplasma chamber to a same potential while the reactive plasma is presentin the plasma chamber; and rotating the substrate through ninety degreesabout the perpendicular, wherein the angled deposition beam is directedto the substrate through the extraction assembly at the non-zero angleof incidence.
 4. The method of claim 2, wherein the first exposurecomprises scanning the substrate with respect to the extraction assemblyalong the first direction through a first set of etching scans.
 5. Themethod of claim 2, wherein the second exposure comprises scanning thesubstrate with respect to the extraction assembly along the firstdirection through a first set of deposition scans.
 6. The method ofclaim 2, the directing the angled deposition beam comprising: forming asecond reactive plasma in a second plasma chamber, the second plasmachamber comprising a second extraction assembly; setting the substrateand the second plasma chamber to a same potential while the secondreactive plasma is present in the second plasma chamber; andtransporting the substrate from a first adjacent the extraction assemblyto a second position adjacent the second extraction assembly, whereinthe substrate and the second extraction assembly are arranged such thatthe angled deposition beam is extracted through the second extractionassembly and is directed to the second side region.
 7. The method ofclaim 6, the directing the angled deposition beam comprising directingthe angled deposition beam at a second non-zero angle of incidence withrespect to the perpendicular, different from the non-zero angle ofincidence.
 8. The method of claim 6, wherein the reactive plasmacomprises a first reactive chemistry, and wherein the second reactiveplasma comprises a second reactive chemistry.
 9. The method of claim 1,wherein the set of features comprises a set of cavities, wherein, afterthe third exposure, the set of cavities has a second dimension, greaterthan the first dimension along the first direction, and retains thesecond dimension along the second direction.
 10. The method of claim 1,wherein the protective layer and the mask layer comprise a samematerial.
 11. The method of claim 1, wherein the set of featurescomprises a plurality of cavities, wherein after the third exposure, theplurality of cavities are merged to form one cavity.
 12. A method ofpatterning a substrate, comprising: providing a set of features in amask layer, the mask layer being disposed on a surface of the substrateand comprising a first material, wherein a given feature comprises afirst dimension along a first direction, a second dimension along asecond direction, orthogonal to the first direction, and a firstthickness; and repeatedly performing an etch cycle to selectively etchthe set of features, the etch cycle comprising: directing an angled ionbeam to the set of features in a first exposure, when the substrate isoriented at a first twist angle, wherein the set of features is etch afirst amount along the first direction; rotating the substrate to asecond twist angle after the directing the angled ion beam; anddirecting an angled deposition beam to the set of features in a secondexposure, wherein a protective layer is formed on a protected portion ofthe set of features.
 13. The method of claim 12, the directing theangled ion beam comprising: forming a reactive plasma in a plasmachamber; applying a bias voltage between the substrate and the plasmachamber; and extracting the angled ion beam from the reactive plasmathrough an extraction assembly, and directing the angled ion beam as anangled reactive ion beam to the substrate at a non-zero angle ofincidence with respect to a perpendicular to a main plane of thesubstrate.
 14. The method of claim 13, the directing the angleddeposition beam comprising: after the first exposure, setting thesubstrate and plasma chamber to a same potential while the reactiveplasma is present in the plasma chamber; and rotating the substratethrough ninety degrees about the perpendicular, wherein the angleddeposition beam is directed to the substrate through the extractionassembly at the non-zero angle of incidence.
 15. The method of claim 12,wherein the set of features comprise a set of structures that define atleast one cavity, wherein after the first exposure, the set ofstructures are characterized by a depletion zone in a plane orthogonalto the first direction where mask material is removed, and wherein afterthe second exposure the protective layer fills the depletion zone. 16.The method of claim 15, wherein before a given etch cycle, the set ofstructures are characterized by a given shape, a height and a spacing,and wherein after the given etch cycle the given shape, the height andthe spacing are restored for the set of structures.
 17. An apparatuscomprising: a plasma chamber to generate a processing plasma; asubstrate stage, to support a substrate, and disposed adjacent to theplasma chamber; an extraction assembly, disposed along a side of theplasma chamber, between the plasma and the substrate stage, to extractplasma species from the plasma; a bias voltage source to apply a biasvoltage between the plasma chamber and the substrate; and a controllerto send a first control signal to the bias voltage source to apply afirst bias voltage between the plasma chamber and the substrate whilethe substrate stage is arranged at a first twist angle, and to send asecond control signal to the bias voltage source to apply second biasvoltage between the plasma chamber and the substrate, the second biasvoltage being less in absolute magnitude than the first bias voltage,and to send concurrently with the second control signal, a third controlsignal to rotate the substrate stage to a second twist angle.
 18. Theapparatus of claim 17, wherein the extraction assembly comprising anelongated extraction aperture.
 19. The apparatus of claim 17, whereinthe controller is configured to send the first control signal the secondcontrol signal and the third control signal to perform an etch cycle,wherein the controller is configured to repeat the etch cycle accordingto a predetermined recipe.
 20. The apparatus of claim 19, wherein thepredetermined recipe comprises a set of instructions to etch a cavity,characterized by a length, a first height, and a first width, whereinwithin a given etch cycle the predetermined recipe is set to increasethe length of the cavity, while maintaining the first width and thefirst height.